MPC8321E Freescale Semiconductor, Inc, MPC8321E Datasheet - Page 70

• Manufacturer Part Number: MPC8321E
• Description: Mpc8321e Powerquicc Ii Pro Processor
• Manufacturer: Freescale Semiconductor, Inc

Thermal
23.2
For the following sections, P
23.2.1
An estimation of the chip junction temperature, T
where:
The junction-to-ambient thermal resistance is an industry standard value that provides a quick and easy
estimation of thermal performance. As a general statement, the value obtained on a single layer board is
appropriate for a tightly packed printed-circuit board. The value obtained on the board with the internal
planes is usually appropriate if the board has low power dissipation and the components are well separated.
Test cases have demonstrated that errors of a factor of two (in the quantity T
23.2.2
The thermal performance of a device cannot be adequately predicted from the junction-to-ambient thermal
resistance. The thermal performance of any component is strongly dependent on the power dissipation of
surrounding components. In addition, the ambient temperature varies widely within the application. For
many natural convection and especially closed box applications, the board temperature at the perimeter
70
Junction-to-package top
Notes:
1. Junction temperature is a function of die size, on-chip power dissipation, package thermal resistance, mounting site (board)
2. Per JEDEC JESD51-2 with the single layer board horizontal. Board meets JESD51-9 specification.
3. Per JEDEC JESD51-6 with the board horizontal.
4. Thermal resistance between the die and the printed-circuit board per JEDEC JESD51-8. Board temperature is measured on
5. Thermal resistance between the die and the case top surface as measured by the cold plate method (MIL SPEC-883 Method
6. Thermal characterization parameter indicating the temperature difference between package top and the junction temperature
temperature, ambient temperature, air flow, power dissipation of other components on the board, and board thermal
resistance.
the top surface of the board near the package.
1012.1).
per JEDEC JESD51-2. When Greek letters are not available, the thermal characterization parameter is written as Psi-JT.
MPC8323E PowerQUICC™ II Pro Integrated Communications Processor Family Hardware Specifications, Rev. 1
T
T
R
P
A
J
θ
D
Thermal Management Information
JA
= junction temperature (°C)
= ambient temperature for the package (°C)
= power dissipation in the package (W)
Estimation of Junction Temperature with Junction-to-Ambient
Thermal Resistance
Estimation of Junction Temperature with Junction-to-Board
Thermal Resistance
Characteristic
= junction-to-ambient thermal resistance (°C/W)
T
J
= T
A
Table 64. Package Thermal Characteristics for PBGA (continued)
+ (R
θ
JA
D
= (V
× P
D
DD
)
× I
DD
Natural convection
) + P
Board type
I/O
J
, can be obtained from the equation:
, where P
I/O
is the power dissipation of the I/O drivers.
Symbol
Ψ
JT
J
– T
Value
A
2
) are possible.
Freescale Semiconductor
°C/W
Unit
Notes
6